Barreter wire unit



Jan. 21, 1947. WEBBER 2,414,499

BARRETER WIRE UNIT Filed Dec. 15, 1943 I' wil Igllllll 'INVENTOR f/ua/l E. WfBBER A'ITORNEY Patented Jan. 21, 1947 BABBETEB WIRE UNIT nun n. Webber, Williston Park; N. r., assignor to Sperry Gyroscope Company, Inc.,a corporation of New York Application December 1:, 194:, Serial No. 514,108

8 Claims. (Cl. 201-64) The present application is a continuation-inpart of my copending application. Serial No. 513,164, filed December 6, 1943.

The present invention relates to alternatins current power-measuring apparatus, and concerns particularly Barreter wire units for microwave wattmeters and methods for producing the same.

It is an object of my invention to provide an improved, sturdy, durable wholly-enclosedresistance wire unit which may be used as a Barreter wire in microwave apparatus.

Another object of the invention is to provide a simplified, inexpensive, expeditious method of producing enclosed resistance, wire units,

Still another object of the invention is to provide insulated-body wire units having low-loss at high frequencies.

Other and further objects and advantages will become apparent as the description proceeds.

In carrying out the invention in its preferred form, resistance wire composed of a suitable material such as platinum is inserted in a length of fine-bore tubing or vitreous insulating material, such as glass or quartz, for example. and the tubing and wire core are together drawn out to form a fine resistance wire enclosed in the insulating tubing substantially fused to the wire. The drawn tubing is then cut into pieces of appropriate lengths, and metallic terminals are formed at the ends of the pieces to form Barreter wire units.

To form a microwave wattmeter, a holder is provided for holding such a unit in the field produced by microwave energy to be measured, and

direct current is simultaneously supplied to the Barreter wire unit. The direct current'strength is varied to maintain constant power consumption and resistance of the Barreter wire. The microwave power is determined by measuring the variation in direct current power required to maintain constant power dissipation.

A better understanding of the invention will be attorded by the following detailed description considered in conjunction with the accompanying drawing in which:

Fig. 1 is a schematic diagram of a bridge circuit which may be employed in conjunction with an alternating current wattmeter of the Barreter wire type;

Fig. 2 is a side view partially in section of a z in the process of producing a Barreter wire uni in accordance with my invention;

Fig. 4 is a perspective view representing a further step in the process of forming the Barreter wire unit; I

Fig. 5 is a perspective view illustrating a more advanced step in the process of forming the Barreter wire unit;

Fig. 6 is a fragmentary sectional view showing the end of the Barreter wire unit in its condition as represented in' the step of the process in Fig. 5;

Fig. 7 is a view corresponding to Fig. 6, illustrating the appearance of the unit after an ad- I ditional step in the preparation of the unit;

Fig. 8 is a view corresponding to Fig. '7, illustrating the condition after the end-of the wire has been coated;

,Fig. 9 is a view corresponding to Fig. 8, illustrating the condition of the unit after the end of the unit has been coated to form an end terminal or ferrule; and

Fig. 10 is a side view of Barreter wire unit in its completed form. 7 Like reference characters are utilized throughout the drawing to designate like parts.

As described in greater detail in my above mentioned parent application, a direct-current bridge such as shown in Fig. 1 may be employed for maintaining constant the resistance of a Barreter were under varying conditions of microwave power input for the purpose of measuring the microwave power by measuring variations in the direct current powers. Summarizing, such a bridge comprises four bridge arms I I, l2; l3 and N, with a diagonal arm I! and a direct current power supply source ii. The arms H and I2 may be standard resistors, the arm l3 includesa resistor and a current-responsive instrument such as a milliammeter in series forming a single arm of the bridge, and the arm I4 comprises a Barreter wire unit, an improved form of which will be described in greater detail hereinafter in the specification. This unit is characterized by .form of wire holder which may be employed for the fact that it has a high change in resistance for a change in temperature.

The arm l5 includes a null galvanometer l1 and a sensitivity adjuster rheostat l8 connected in series. For controlling the direct current'power input to the bridge, rheostats l9 and a switch 2| are connected in series with the direct current supply source It.

The actual resistance constituting the arm H of the bridge consists of a length of wire or filanient composed of suitable material such as platinum mounted and enclosed 'within 2. protect- 7 .power from the microwave field, ,or tocor ,ultra high frequency current without producing ing and insulating body such as atube 22 comanda tubular-extending portion t2, the length posed of a vitreous material such as glass or I4 and conducting'end terminals or ferrules 23 are provided which are in electrical contact with a the ends of the wire Id. The Barreter wire with its enclosing tube and 'end terminals'forms a" removable and 'lnterchangeable Barreter wire unit 24, which may be so mounted as to absorl;

reflections in the field. For so mounting the Barreter wire unit, suitable wire holders are provided, for example, a wire hoider of one of the types disclosed in my copending applications Serial No. 5l3,l 64, flied December 6, 1943, or Serial No. 514,111, flledDecember 13, 1943.

-- Where the microwave power to be measured. is supplied through a wave s idetype of transmission line, the wire holder may takethe form" illustratedmFig.2,ior example. 7

The wire holder of Fig. 2 comprises a wave guide 26 open at the lefthand end with achoke coupling 21 mounted thereon, adapted to make connection with an input wave guide (not shown) having a similar choke coupling to be attached to the choke coupling 21. Suitable sockets 28 and of which is substantially a quarter-wave or the wave length for which the wave guide as is designed.

' The socket connector rod 29 is provided with a flange st for supporting the rod 29 centrally of the tube 52, and a connector housing 36 is pro- 29 are provided for holding the unit 24 athwart the wave guide 26 and making electrical connections to a bridge, such as that shown in Fig. 1.

For timing the line and matching the impedance of the wave guide transmission line 26 to that of the Barreter wire M, a line-length-adlusting mechanism 3|, and tin-adjustable stub. line 32 are provided. The line-adjusting mechanism 3i comprises a rotatable screw 38 carrying at its inner end a shorting plug (not shown) 28 s: adjusted by the screw 23.

1 Although my invention is not limited to the use the longitudinalposition of which within the line i tubing to tend to fuse of Barreter wires in a particular typeot wave guide, it is assumed for the sake of illustration that the wave guide shown in Fig. 2 is a rectanular hollow pipe type having the wide'transverse dimensions perpendicular to the plane' of the drawing and the narrow transverse. dimension in the plane of the drawing.

I drawn to a large scale and in 'tional view in'Fig. 6. It will be observed that The stub line 32 as illustrated is of the coaxial visible) for forming a spring socket to hold. the

upper conducting terminal 23 of the unit 2%.

The socket 29 consists of a metallic rod'drilled in a similar manner to form a socket for the lower end of the unit 24, but insulated from the wave guide 26. An opening is formed in the lower wall of the wave guide 26 to receive the socket 29 and the opening is made ofsumcient size to leave an annular clearance space-88. Preferably a quarter-wave trap i mounted around the clearance opening 38. Such a trap may be formed by a flanged tubular member 39 having a flange ll fitted into the lower wall 01' the wave guide 28 type having an outer hollow right-circular cylinder 34 joined to the edges of anopening formed wire it through the stub line members sufliciently, an

the pin 48 is grounded to the wave guide 26 so 1 as to provide a circuit to the upper end of the 8s and as.

For forming the Barreter wire unit 34!, a length 01' wire it (Fi 3) is passed through the bore of aflne-bore vitreous tube 52. The tube as may be of suitable material such as glass or quartz, preferably the latter, for forming low-loss microwave wattmeters and the tubing is heated to the point of softening by suitable means. Such means are represented schematically by a fish-tail burner 53 producing an elongated flame 55,111.11) it willbe understood thst for softening quartz v oxyhydrogen blowpipe will be required; r

When the tubing material has been softened by the heat of the 52 and thepwire 5i are simultaneouslydrawn apart so as to draw down the wire and the center of the tubing stock may beseparated a little further after the wire St has been drawn down to the desired diameter so as to cause the quartz to the wire 5i. After the wire 5i and the reduced diameter portion 56 of the tubing is cut into a plurality of shortlengths 51 as shown in Fig. 5. One end of such a length is shown a relativelyistraight fracture occurs, forming the square end 58. In order to provide for making good electrical, contact with the end 59 of the wire, the end 58 of the quartz is preferably etched away to form the and shape shown in Fig. '7. This may be accomplished by dipping'the end of the piece 57 in a suitable reagent-reacting more quickly upon the quartz than the wire 59,

such-as a mixture of hydrofluoric acid and nitric acid. for example, in mately 70% and 30%. a

Preferably the tip 59 is coated with a highconductlvlty electric-conducting material such proportions of approxi as silver or copper to form an end coat iii as illustrated in Fig. 8. However, ii desired, a layer of platinum may be coated on the end 59.. The coating 6i may be deposited in any desired manner by eleetro-deposition in an elastic-plating cell (not shown).

Aiter the wire end coating ti has been deposited, a heavier conducting coating of suitable material is preferably deposited on the end of the tubing 22 to form the unit terminal or ferrule 28. The ferrule or depositedcoating 23 may "be placed on the tubing 22 in any desired manner, for example, the end of the quartz may first be dipped into a suitable mucilaginous material theme at, the ends'of the tube tubing 52 have cooled,

a longitudinal seeoi tubing.

5 such as Bakelite varnish, dusted with graphite,

and then placed in an electro-plating cell ior a coating It.

It will be understood that while the coating is is being deposited at one ending the unit, the wire end coating such as is attiie other end oi the wire it may be utilized for making the r quisite electricalconnections ior the electro-plating process.

After the ilrst end has been iull: coated. the coating 23 at one end will, oi course, serve as the electrical connections ior causing electrodeposition oi the coating 2! at the other end. so that the finished unit 2| has coated terminals 23 at both ends, as shown in Fig. 10.

In accordance with the provisions oi the patent statutes a specific iorm oi apparatus embodying the invention and an illustrative method oi producing apparatus in accordance with the invention have been described, but it is to be understood that the arrangements described are only illustrative and that the invention is not limited to the speciiic apparatus and method described andillustrated. what is claimed is:

1. A Barreter wire unit. comprising a length oi drawn fine-bore tubing oi insulating material. a wire drawn within said tubing. the ends oi the tubing being sealed to the wire, conducting coatings on the ends oi the wire. and terminals deposited at the ends oi the tubing making elec, trical contact with the coatings at the ends oi the wire.

2. A method oi iorming a Barreter wire unit which comprises enclosing a length oi resistance wire in a length of tubing, soitening and drawing down the tubing and enclosed wire, cutting the drawn tubing and wire into shorter lengths, and capping the ends oi the shorter lengths with conducting material making electrical contact withthe endsoithewireineachshorterlensth which comprises surrounding a length oi reislst- 3. A method of iorming a Barreter wire unit which comprises the steps oi drawing a length oi insulating tubing with a metallic core to a reduced diameter, cutting oi! the ends oi the tubing to iorm a unit with substantially squared A ends, etching away the ends oi the lengthioi tubing to expose the ends oi the wire, and coat- Y ing the ends oi the tubing incontact with the ends oi the wire to iorm terminals for the resistance wire unit.

4. A method oi iorming a resistance wire unit ance wire with a length oi insulating tubing. and simultaneously drawing both said wire and said tu ing.

5. A method oi iorming a resistance wire unit which comprises surrounding a length oi resist; ance wire with a length oi insulating tubing, aimultaneously drawing both said wire and said tubing until said wire has -a desired diameter,

and then drawing'only said tubing to flt said 8. A method oi iorming a fine electric currentconducting wire unit which comprises the steps 'oi enclosing a length oi metal wire in a length oi tubing, heating said tubing and enclosed wire. and deforming said tubing and wire to increased length and decreased diameter.

7. A method oi iorming a ilne wire unit which comprises the steps oi enclosing a length oi wire oi a iirst material in a length oi tubing oi a second material, plasticizing said tubing, and deiormingsaid tubing to increased length and de-' creased diameter to provide radial compression and deiormation and increased length of said wire. Y

8. A method oi io'rming a nne wire unit which comprises the steps oi enclomng a length of wire oi a first material in a length oi tubing oi a second material, softening said tubing and wire, and deiorming said tubing and wire coniormally to provide increased length and reduced diameter oi said tubing and wire.

nuannwnnnm 

